1. Field of the Invention
The present invention relates to a method of inserting a pile board into the sheet piling unit of the sheet delivery unit of a sheet-fed printing press, and a pile board inserting machine for carrying out the same.
2. Description of the Prior Art
A pile delivery operation is performed during the printing operation of a sheet-fed printing press to remove printed sheets piled on a pile board from the delivery unit of the printing press without stopping the printing operation, or, to remove a pile of a predetermined number of printed sheets from the delivery unit of the printing press without stopping the printing operation.
A pile board is lowered automatically as printed sheets are delivered successfully onto the pile board. Upon the delivery of the last printed sheet of a predetermined number of printed sheets onto the pile board, the pile board loaded with the printed sheets is lowered by a small distance, and then another pile board is inserted into the sheet piling unit above the pile of the printed sheets on the loaded pile board. The number of printed sheets to be piled on one pile board is determined so that an excessive pressure cannot act on the lower printed sheets and cause set off.
When the printing press is provided with a single sheet piling unit, a new pile board must be inserted quickly into the sheet piling unit in synchronism with the operation of the printing press which then is operating at a high printing speed, and which requires skilled work.
The frequency of pile board insertion increases with an increase in the printing speed of the printing press, thus increasing physical and metal load on the operator. Furthermore, if a pile board inserted unsuccessfully into the sheet piling unit, the printed sheet may be damaged.
Therefore, the printing speed of the printing press is reduced during the insertion of a pile board onto the delivery path, or, the printing press is operated continuously at a comparatively low printing speed when sheets of a large lot are to be printed, and frequent pile board insertion is necessary.